Apparatus for reading a color symbol

ABSTRACT

The present invention provides an apparatus for reading a color symbol, which comprises a matrix of color filters arranged in front of a detector. Light received from the filters of some colors is used to locate the color symbol, while light received from all the filters is used to read and decode the located symbol. Preferably, the filters used for locating the symbol are of the colors to which the detector is most sensitive. Preferably, the filters for locating the symbol are dominant in number.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to symbol reading and decoding techniques,and more particularly, to apparatus for reading color symbols, such ascolor one and two dimensional barcodes, with higher sensitivity andresolution.

BACKGROUND OF THE INVENTION

Barcodes, with various desired information encoded therein, areuniversally used in many circumstances. There are many types ofbarcodes, such as 1-D barcodes stacked barcodes, 2-D barcodes, etc.These barcodes are usually monochrome symbols that are encoded withinformation in specified patterns of barcode elements (or cells) of twosharply contrasted colors such as black and white. To increase the“information density” (i.e., the information included in the limitedsymbol area), various colors are also used as the barcode elements as incolor barcodes. The color barcodes are usually also read by monochromereaders which identify different colors by different levels ofelectrical signals generated from light reflected from the symbolelements of different colors. However, the sensitivity and resolution ofreading color symbols by monochrome readers is not satisfactory,especially when the color symbols are buried in a colorful backgroundsuch as a color picture.

One technique of reading such color symbols employs plural primary colorfilters, such as Red-Green-Blue filters. A drawback of such anarrangement is that significant loss of sensitivity results from thefiltering of the light reflected from the symbol.

Therefore, there exists a need for a reading system that can read acolor symbol with high sensitivity and resolution, even if the colorsymbol is buried in a colorful background.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for reading a color symbol,which comprises a matrix of color filters provided in front of adetector. According to the teachings of the present invention, lightreceived from the filters of some colors is used to locate the colorsymbol, while light received from other filters or all the filters isused to read and decode the located symbol.

Preferably, the colors of the filters used for locating the symbol arein the range of wavelengths at which the detector is most sensitive.Preferably, the filters for locating the symbol are of the same color,which is preferably of a wavelength of the detector.

Preferably, the pattern of the filters for locating the symbol is of azigzag pattern, which is a part of the whole filter matrix.

Preferably, one color of filters is used to locate the symbol, and allthe filters are used to decode it.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an exemplary color symbol readingsystem according the concept of the present invention;

FIG. 2 illustrates a matrix of filters of an embodiment according to thepresent invention; and

FIG. 3 illustrates a zigzag line resulted from the zigzag pattern of thedominant color filters in the matrix of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the color symbol reading apparatus according to thepresent invention is schematically illustrated in FIG. 1, whichgenerally comprises a light source 14 (such as LED) for projecting light1 to a color symbol (such as a color barcode) 20, a detector 11 forreceiving light 2 reflected from the symbol 20 and for generatingelectrical signals from the received reflectance light 2, an amplifiercircuitry 12 for amplifying the signals generated by the detector 12,and a decoding circuit 13 for decoding the amplified electrical signalsreceived from the amplifier circuitry 12 to obtain a reading result.

According to the present invention, a color filter array (CFA) or filtermatrix 10 which comprises filters of various colors is provided in frontof the detector 11 for filtering the reflectance light 2 before it isreceived by the detector 11. Only the light passing the filters of some(but not all) colors are utilized to locate the color symbol 20, whilethe light passing all the filters are utilized to read and decode thesymbol 20.

An exemplary embodiment of the filter matrix 10 is illustrated in FIG.2, which comprises filters of three different colors, i.e., the threecomponent colors Cyan, Yellow, Magenta of CYM color system, which isexpected to pass through more light than RGB filter system. In FIG. 2,yellow filters are represented by “white” squares 15, cyan filters by“gray” squares 16, and magenta filters by “dark” squares 17. Forclarity, only some of the filters are designated by reference numbers15, 16 and 17.

Noticeably in FIG. 2, yellow filters 15 are dominant in numberthroughout the area of the filter matrix 10. In the example here, thereare twice as many filters of yellow color as of each of the other twocolors. The yellow filters 15 subtract blue color in principle and passother spectrum of light onto the detector 11. In this preferredembodiment, the reflectance light 2 that passes the yellow filters 15 tobe received by the detector 11 is utilized to locate the colored symbol20. The symbol 20 is located as a whole symbol block but not by symbolelements. In this embodiment, detector 11 has a dominant sensitivity forthe colors passing through the yellow filter. Thus, a high sensitivityof the detector in locating the color symbol 20 is achieved.

After the color symbol 20 is located by the light 2 passing the yellowfilters 15, the light 2 that passes all the color filters 15, 16 and 17in the filter matrix 10 is utilized to read and decode the coloredsymbol 20, which achieves a higher resolution as compared to prior colorsymbol readers.

In order to calculate run-length with minimum noise, pixels of the samecolor should be used. To this end, as illustrated in FIG. 2, thedominant yellow filters 15 are preferably arranged in the filter matrixin a zigzag pattern both horizontally and vertically. This generates azigzag line 15 a (see FIG. 3) for calculating run-length with minimumnoise. Once a finder of the barcode or color symbol 20 is found, thecolors of the symbol 20 can be then evaluated, which is useful forremaining processing of the symbol 20.

Though the yellow filters 15 are utilized as the dominant color filtersin the preferred embodiment illustrated in FIG. 2, any other color (suchas cyan or magenta) may also be used as a dominant color to locate thecolored symbol 20. Preferably, the detector 11 has the most sensitivityfor the wavelength of the same color of the dominant color filter, or isthe most sensitive to the color of the dominant color filters.

Other color systems can also be utilized. For example, filters can havered, green and blue colors as in an RGB color system, with one (e.g.,red) of the colors as the color of the dominant filters for locating thesymbol 20. Filter matrices containing more than three types of filterscould also be employed. It is desirable, although not critical to thepresent invention, that the wavelength at which the detector 11 is mostsensitive and the filter used to locate the symbol have similarwavelengths, in order to maximize the sensitivity.

Alternatively, the matrix filters 10 may comprise more than three colorsand the filters for locating the symbol 20 may comprise more than onecolor (such as yellow in FIG. 2). For example, the filters for locatingthe symbol 20 may comprise filters of several different colors. If so,the colors are preferably close to each other and the detector 11 ismore sensitive to them than other colors.

Though the above describes the preferred embodiments of the presentinvention, it will be appreciated that, without departing the spirit ofthe present invention, numerous adaptations, variations andmodifications are readily available to a person with ordinary skill inthe art. For example, the color filters 15, 16, 17 can be of other typesof patterns other than that shown in FIG. 2, such as honeycomb pattern.The color symbol 20 can be a linear barcode of any dimension, a stackedbarcode, a matrix barcode, etc., buried in a colorful background or not.The filters used for locating the color symbol 20 may or may not bedominant in number as compared to other filters. Therefore, the scope ofthe present invention is intended to be solely defined in theaccompanying claims.

1-4. (canceled)
 5. An apparatus for finding and decoding a symbolcomprising a matrix of light filters of plural wavelengths, whereinlight received through filters of a first set of said wavelength filtersis used for locating the symbol to be read, and light received through asecond set of said filters is utilized to read or decode said symbol;wherein said first set is less than all of the filters and wherein saidsecond set includes all of the filters.
 6. Apparatus of claim 5 whereinsaid first set is comprised of filters that are all of the samewavelength.
 7. Apparatus of claim 6 wherein said first set of filters iscomprised of Yellow filters.
 8. Apparatus of claim 6 wherein said firstset of filters forms a zig-zag pattern.
 9. Apparatus for reading a colorsymbol comprising patterned arrangement of filters of plural colors, andsoftware for first processing light received through less than all ofsaid filters to locate the color symbol, and then processing lightreceived through all filters to decode said color symbol.
 10. Theapparatus of claim 9 wherein the light received through less than all ofthe filters is of a wavelength to which a detector located behind saidfilters is more sensitive than said detector is to light receivedthrough the remaining filters.
 11. The apparatus of claim 9 wherein thepattern is a matrix and the filters to which said detector is moresensitive all allow passing of substantially the same wavelength oflight.
 12. The apparatus of claim 11 wherein filters of one dominantcolor occupies a zig-zag pattern within said matrix, and filters of atleast two other colors occupy remaining portions of said matrix.
 13. Anapparatus for reading a color symbol comprising an arrangement offilters of at least three colors, wherein filters of a first of saidthree colors occupy more of said arrangement than filters of a secondand third colors, and wherein filters of said first color are used tolocate said symbol being read.
 14. The apparatus of claim 13 whereinsaid filters of a second and third color are used to read said locatedsymbol.
 15. The apparatus of claim 14 wherein filters of said first,second, and third colors are used to read said located symbol.
 16. Theapparatus of claim 15 wherein said filters are of the colors Cyan,Yellow, and magenta, and wherein said filter of said first color isyellow. 17-20. (canceled)